Lead-acid battery

ABSTRACT

The present invention provides a lead-acid battery superior in high-efficiency charging characteristic to conventional lead-acid batteries; and a carbon material used in the lead-acid battery, having excellent charge acceptability. That is, the present invention provides a lead-acid battery which uses, as an additive to the anode active material, a simple substance and/or a compound thereof, both having a catalysis for desulfurization or a catalysis for SO x  oxidation by adding to or loading on a carbon material such as active carbon, carbon black or the like and thereby has superior high-efficiency charging characteristic and improved charging acceptability. When such a lead-acid battery whose anode contains a carbon material containing or loading thereon the above simple substance and/or compound, is applied to electric cars, various hybrid cars, power storage systems, elevators, electromotive tools and power source systems such as uninterruptible power source, distributed power source and the like, all having high input and output requirements, stable control can be obtained.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a lead-acid battery,particularly a carbon material for a lead-acid battery superior inhigh-efficiency charging characteristic.

[0003] 2. Related Art Statement

[0004] A lead-acid battery as a secondary battery is relativelyinexpensive and has stable properties; therefore, has been widely usedas an electric source for automobiles and portable apparatuses, or as aback-up electric source for computers. Recently, a lead-acid battery hasfound new applications as a main electric source for electric cars, asan electric source for start-up of hybrid electric cars and simplehybrid cars, or for recovery of regenerated current. In these newapplications, a lead-acid battery need to have, in particular, both ofhigh output characteristic and high input characteristic.

[0005] Various studies have heretofore been made on the high outputcharacteristic. With respect to the high input characteristic, however,there has been obtained no level which is superior to those of otherbattery systems.

[0006] The high input characteristic, i.e. high-efficiency chargingcharacteristic of a lead-acid battery is greatly influenced by thecharacteristics of the lead sulfate present in the anode. With respectto the anode active material of a lead-acid battery, metallic lead emitselectrons and is converted into lead sulfate in the discharge reaction;in the charging reaction, lead sulfate accepts electrons and isconverted into metallic lead. The lead sulfate generated duringdischarge has neither ionic conductivity nor electron conductivity andis an insulating material. Further, the lead sulfate is very low insolubility into lead ion. Thus, lead sulfate is low in electron or ionicconductivity and moreover low in solubility into lead ion; therefore,the rate of reaction from lead sulfate into metallic lead is small,resulting in inferior high-efficiency charging characteristic.

[0007] As countermeasure therefor, improvements of chargingcharacteristic have been tried, for example, by optimizing the amount ofcarbon added into an anode active material (JP-A-9-213336) or byallowing an anode active material to contain metallic tin(JP-A-5-89873).

OBJECT OF THE INVENTION

[0008] In order to obtain an improved high-efficiency chargingcharacteristic, the properties of lead sulfate need be improved. Thatis, it is necessary to firstly improve the conductivity of lead sulfateand secondly increase the solubility of lead sulfate into lead ion. Theimprovement of the electron conductivity and ionic conductivity of leadsulfate is possible by addition of an optimum amount of carbon, as seenin JP-A-9-213336. With this addition of an optimum amount of carbon,however, it is impossible to improve the solubility of lead sulfate intolead ion. Similarly, by allowing an anode active material to containmetallic tin, the conductivity improvement of lead sulfate is possiblebut the improvement of solubility of lead sulfate into lead ion isimpossible.

[0009] The objects of the present invention are to provide

[0010] a lead-acid battery of superior high-efficiency chargingcharacteristic wherein the conductivity of lead sulfate is improved andfurther the solubility of lead sulfate into lead ion is improved andthereby the charging reaction of anode active material proceedssmoothly, and

[0011] a novel carbon material superior in charge acceptability.

SUMMARY OF THE INVENTION

[0012] Firstly, the lead-acid battery of the present invention ischaracterized in that a carbon powder containing a simple substanceand/or a compound, both having a catalysis for desulfurization or SO_(x)oxidation is added into the anode. The carbon material for a lead-acidbattery according to the present invention is characterized by being acarbon powder containing a simple substance and/or a compound, bothhaving a catalysis for desulfurization or SO_(x) oxidation. Use of sucha carbon powder can give a lead-acid battery of improved high-efficiencycharging characteristic. The high-efficiency charging characteristic ofa lead-acid battery is improved strikingly when a carbon containing asimple substance and/or a compound, both having, in particular, acatalysis for hydrogenation desulfurization is added.

[0013] When the simple substance and/or the compound, both having acatalysis for desulfurization is at least one major componentconstituting catalysts for desulfurization or deodorization selectedfrom catalysts for petroleum refining, catalysts for fuel oildesulfurization, catalysts for gas production and catalysts forpollution control, the resulting lead-acid battery can have a furtherimproved high-efficiency charging characteristic.

[0014] The above component is desirably at least one simple substanceselected from Co, Mo, Ni, Zn, Cu and Mn, or at least one oxide, sulfateor hydroxide thereof.

[0015] Also when the simple substance and/or the compound, both having acatalysis for SO_(x) oxidation is at least one major componentconstituting catalysts for sulfuric acid production, the resultinglead-acid battery can have an improved high-efficiency chargingcharacteristic. A simple substance or compound which can be convertedinto a sulfate, is preferred particularly.

[0016] The above component is desirably at least one simple substanceselected from alkali metals, alkaline earth metals, V, Mn and rare earthelements, or at least one oxide or sulfate thereof.

[0017] Secondly, the lead-acid battery of the present invention ischaracterized in that the following loaded material is added into theanode. That is, there is added, into the anode, a loaded materialobtained by loading, on a carbon powder, at least one simple substanceselected from Hf, Nb, Ta, W, Ag, Zn, Ni, Co, Mo, Cu, V, Mn, Ba, K, Cs,Rb, Sr and Na, desirably from Ni, Co, Mo, Cu, V, Mn, Ba, K, Cs, Rb, Srand Na, or at least one oxide, sulfate, hydroxide or carbide thereof. Byusing such a loaded material, the resulting lead-acid battery can havean improved high-efficiency charging characteristic.

[0018] When said at least one element is loaded on the carbon in anamount of 10 to 5,000 ppm, desirably 50 to 1,000 ppm by weight perelement, the resulting lead-acid battery can have a further improvedhigh-efficiency charging characteristic.

[0019] In the present lead-acid battery, by using, as the carbon, atleast one member selected from carbon black, acetylene black, naturalgraphite, artificial graphite, pyrolytic carbon, coke, isotropicgraphite, mesophase carbon, pitch-based carbon fiber, carbon fiber byvapor phase growth, carbon fluoride, nanocarbon, active carbon, activecarbon fiber and PAN-based carbon fiber, a superior high-efficiencycharging characteristic can be obtained. Some of these carbons havevarious primary particle diameters, various specific surface areas,various oil absorptions as measured with dibutyl phthalate, or variousapparent densities, but the present invention is applicable to all ofthese carbons.

[0020] The simple substance or compound loaded on the carbon powderdesirably has an average primary particle diameter of 0.1 to 1,000 nm.This average primary particle diameter is an average primary particlediameter obtained by observation using a transmission electronmicroscope. The primary particle diameters of the loaded material differdepending upon the firing conditions used, such as firing temperature,firing atmosphere and the like. For example, a loaded material having anaverage primary particle diameter of the above range is obtained at afiring temperature of about 300° C. when the firing atmosphere is air,about 350° C. when the atmosphere is nitrogen, and about 370° C. whenthe atmosphere is hydrogen.

[0021] Thirdly, the lead-acid battery of the present invention ischaracterized in that the following active carbon and/or carbon black isadded into the anode. That is, there is added, into the anode, an activecarbon and/or carbon black containing at least one simple substanceselected from Cu, Ni, Zn, Mn, Al, Si, K and Mg, or at least one compoundthereof. The carbon material for use in a lead-acid battery according tothe present invention is characterized by being an active carbon and/orcarbon black containing at least one simple substance selected from Cu,Ni, Zn, Mn, Al, Si, K and Mg, or at least one compound thereof. Activecarbon or carbon black has a complicated pore structure. The porescontain various impurities. By using, in particular, an active carbon orcarbon black containing, as impurities, at least one simple substanceselected from Cu, Ni, Zn, Mn, Al, Si, K and Mg, or at least one compoundthereof, a lead-acid battery of improved high-efficiency chargingcharacteristic can be obtained.

[0022] The active carbon is desirably an active carbon produced fromcoconut husk, having a Cu content of more than 5 ppm by weight but lessthan 15,000 ppm by weight. Since coconut husk which is a naturalproduct, contains Cu, Mn, Al, Si and K, the active carbon producedtherefrom contains the above elements in a large amount. When the activecarbon contains, in particular, Cu in an amount of more than 5 ppm byweight but less than 15,000 ppm by weight, the anode of the resultinglead-acid battery can be improved significantly in high-efficiencycharging characteristic as well as in charge acceptability.

[0023] The carbon black is desirably a furnace black having a totalcontent of Ni, Cu, Zn and Mn more than 1 ppm by weight but less than1,000 ppm by weight. Since fuel oil contains impurities such as Ni, Cu,Zn and Mn in a large amount, the furnace black produced therefrom alsocontains the above elements in a large amount. When the furnace blackcontains, in particular, Ni and Cu in a total amount of more than 1 ppmby weight but less than 1,000 ppm by weight, the anode of the resultinglead-acid battery can be improved significantly in high-efficiencycharging characteristic as well as in charge acceptability.

[0024] Lastly, the carbon material for use in a lead-acid batteryaccording to the present invention is characterized by being a carbonpowder containing or loading thereon at least one simple substanceselected from Hf, Nb, Ta, W, Ag, Zn, Ni, Co, Mo, Cu, V, Mn, Ba, K, Cs,Rb, Sr and Na, or at least one oxide, sulfate, hydroxide or carbidethereof. The carbon powder may be added into the electrolytic solutionof a lead-acid battery or onto the surface of an electrode, whereby thestart of charging can be accelerated. The loading of the simplesubstance or the oxide, sulfate, hydroxide or carbide thereof can beconducted desirably by wet loading.

[0025] Other objects, features and advantages of the invention willbecome apparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a drawing showing an embodiment of the presentinvention.

[0027]FIG. 2 is a graph showing the relation between Ni content (ppm)and charging voltage (Vc) in the case of using the nickel-loadedacetylene black obtained by firing in air, in Example 1 of the presentinvention.

[0028]FIG. 3 is a graph showing the relation between firing temperatureand charging voltage (Vc) in the case of using the nickel-loadedacetylene black obtained by firing in nitrogen, in Example 1 of thepresent invention.

[0029]FIG. 4 is a graph showing the relation between firing temperatureand charging voltage (Vc) in the case of using the nickel-loadedacetylene black obtained by firing in hydrogen, in Example 1 of thepresent invention.

[0030]FIG. 5 is graphs showing the relations between the loaded amountof loaded elements and charging voltage (Vc), obtained in Example 5 ofthe present invention.

[0031]FIG. 6 is a drawing showing a model of the catalysis fordesulfurization in Example 7 of the present invention.

[0032]FIG. 7 is a drawing showing a model of the catalysis for SO_(x)oxidation in Example 7 of the present invention.

[0033]FIG. 8 is graphs each showing the current-potential characteristicobtained in Example 8 of the present invention.

[0034] The numerals in FIG. 1 refer to the followings.

[0035]1: anode plate; 2: cathode plate; 3: separator; 4: group ofelectrodes; 5: cathode strap; 6: anode strap; 7: battery case; 8:cathode terminal; 9: anode terminal; 10: cover

DETAILED DESCRIPTION OF THE INVENTION

[0036] According to the present invention, a lead-acid battery can beprovided which shows a small energy loss caused by gas generation evenduring large-current (2C or more) charging and which has an improvedhigh-efficiency charging characteristic. Here, 2C is a current valuenecessary to discharge the total discharge capacity of a battery in 0.5hour, and 1C is a current value necessary to discharge the totaldischarge capacity of a battery in 1 hour.

[0037] The present invention is characterized by utilizing an actiontoward sulfur (S) commonly possessed by catalysts, for example, strongadsorbability for sulfur (S) possessed by the component contained in acatalyst. In desulfurization of, for example, crude oil, desulfurizationof thiophenes has been generally well known. In desulfurization ofbenzothiophene, the S in benzothiophene is adsorbed on the active sitesof the catalyst used and hydrogenated to become H₂S, which is eliminatedas such; in this way, a desulfurization reaction proceeds. This appliesalso to the elementary reaction of charging in the anode of a lead-acidbattery, that is, a reaction in which lead sulfate is dissociated intosulfate ion and lead ion. That is, the sulfate group in lead sulfate isadsorbed on the active sites of the catalyst and hydrogenated to becomeHSO₄ ⁻, which is released into the electrolytic solution as such. In thecase of a lead-acid battery, since the sulfuric acid concentration inthe electrolytic solution is as high as 30% by volume, dissociation inthe form of SO₄ ²⁻ is impossible and the most part of SO₄ ²⁻ isdissociated in the form of HSO₄ ⁻. Thus, diffusion in the form of HSO₄ ⁻is important in order to increase the solubility of lead sulfate.

[0038] Meanwhile, in catalysts used for sulfuric acid production, thereare mainly used components capable of taking SO_(x) into the respectivemolecules and converting it into a sulfate of higher degree. V₂O₅ andsulfates of Rb, K, Cs, etc. are known to take SO_(x) into the respectivemolecules and convert it into VOSO₄ or Me₂S₂O₇ (Me is Rb, K or Cs). Thisapplies also to the elementary reaction of charging in the anode of alead-acid battery, that is, a reaction in which lead sulfate isdissociated into sulfate ion and lead ion. The above oxide or eachsulfate takes dissociated sulfate ion into the molecule and thereby canpromote dissolution.

[0039] The anode of the present invention is characterized in that thereis added, into the anode, a carbon containing a simple substance or acompound, both having a particular catalysis, for example, a catalysisfor desulfurization, a catalysis for SO_(x) oxidation or a catalysis forsulfuric acid production. Carbon is an essential substance forincreasing the conductivity of lead sulfate, but no sufficient chargingcharacteristic is obtained with carbon alone. Therefore, addition of asimple substance or a compound, both having a particular catalysisbecomes necessary. Meanwhile, with addition of only a simple substanceor a compound, both having a particular catalysis, no conductivity suchas obtained with carbon and accordingly no satisfactory high-efficiencycharging characteristic is obtainable.

[0040] In order to obtain a sufficient catalysis, it is desired tohighly disperse, on a carbon, a simple substance or a compound, bothhaving a particular catalysis, in the form of particles of very smalldiameters.

[0041] Some of active carbons or carbon blacks having complicated porestructures, for example, porous structure, fine structure, mesoporestructure, micropore structure, submicropore structure, macroporestructure, structure having inner surface and structure of high specificsurface area, contain, in the pores, a small amount of a simplesubstance or a compound, both having the above-mentioned catalysis. Thisis advantageous for effective utilization of catalysis. Some of activecarbons or carbon blacks have a function of adsorbing various moleculesand ions into the complicated pores. Thus, in the elementary reaction ofcharging in the anode of a lead-acid battery, that is, a reaction inwhich lead sulfate is dissociated into sulfate ion and lead ion, sulfateion is easily adsorbed into the pores of the active carbon. Since thereis present, in the pores, a simple substance or a compound, both havingthe above-mentioned catalysis, sulfate ion is easily converted into HSO₄⁻ or is taken into an oxide or sulfate, whereby charging reactionproceeds smoothly. Carbons produced from natural products or fuel oil,such as active carbon or carbon black and the like, often contain inthemselves a large amount of a simple substance or a compound, bothhaving a catalysis; therefore, by using a carbon obtained by subjectinga natural product-derived carbon to an acid treatment, a heat treatmentor the like to control the concentration of the simple substance orcompound at an optimum range, a superior high-efficiency chargingcharacteristic can be obtained even with no loading on the carbon.

[0042] Further, containing a particular simple substance or compound,both having the above-mentioned catalysis highlky, the carbon powder ofthe present invention, when added into the electrolytic solution or ontothe electrode surface, of a lead-acid battery, can accelerate the startof charging. The carbon can be adsorbed on the reaction interface of theactive material of the lead-acid battery; thereby, the passivation oflead sulfate which is called sulfation can be suppressed, no passivationproceeds even when complete discharge has been made, and chargeacceptability is improved remarkably.

[0043] Thus, by using the anode of the present invention, a lead-acidbattery can be obtained which is applicable as an industrial batteryrequiring a high input characteristic and a high output characteristic,used for electric car, parallel hybrid electric car, simple hybrid car,power storage system, elevator, electric tools, uninterruptible powersource, distributed power source, etc.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0044] The present invention is described in more detail below by way ofExamples. However, the present invention is in no way restricted tothese Examples within the scope of the present invention. In-depthdescription is made on the Examples of the present invention, incomparison with Comparative Examples concerning lead-acid batteriesproduced for confirming the effects of the Examples.

[0045] Description is made first on methods for production of lead-acidbatteries of Examples and Comparative Examples. With respect toproduction methods in Example 2, later Examples and ComparativeExamples, the same procedures as in Example 1 are not described anddifferent procedure portions are described.

EXAMPLE 1 Production of Simple Substance- and/or Compound-Loaded Carbons

[0046] In production of simple substance- and/or compound-loadedcarbons, first, aqueous nickel nitrate solutions of differentconcentrations were prepared. Thereto were added 10 g of acetylene blackas a carbon powder and 0.1 g of a surfactant. Each resulting mixture wasstirred in a water bath of 40° C. Thereto was dropwise added sodiumhydroxide until the pH of each mixture became 7. Then, filtration wasmade. The separated precipitate was washed with distilled water, driedat 120° C. for 2 hours, and fired in the air, nitrogen or hydrogen at300 to 500° C. for 30 minutes to produce various nickel-loaded carbons.XRD (X-ray diffractometry) indicated that NiO was formed by the firingin the air, Ni was formed by the firing in hydrogen, and a mixture ofNiO and Ni was formed by the firing in nitrogen. Incidentally, X-raydiffractometry is a method which measures the intensity of diffractionline while changing the angle of diffraction of X-ray and analyses theangle and the intensity, and is used for analysis of crystal structure.In the X-ray diffraction of the present invention, an ordinary powderdiffraction method was used and a CuK_(α) ray was used as the X-raysource.

[0047] In Table 1 are shown the Ni contents in various Ni-loadedcarbons, as determined by ICP (inductively coupled plasma) spectrometry.Incidentally, ICP spectrometry is a method which can detect a pluralityof elements and determine the quantity simultaneously at a highsensitivity. A sample was placed in an acidic solution of 100° C. ormore (e.g. boiling hydrochloric acid or nitric acid solution); boilingwas conducted for 2 to 3 hours to dissolve the metal in the sample; anddetermination was made for the resulting solution. TABLE 1 Firing FiringNi content Symbol atmosphere temperature (ppm) 1-a Air 300° C. 10000 1-bDitto 300° C. 5000 1-c Ditto 300° C. 1000 1-d Ditto 300° C. 500 1-eDitto 300° C. 100 1-f Ditto 300° C. 50 1-g Ditto 300° C. 10 1-h Ditto300° C. 1 1-i Nitrogen 300° C. 100 1-j Ditto 350° C. 100 1-k Ditto 400°C. 100 1-l Ditto 450° C. 100 1-m Hydrogen 400° C. 100 1-n Ditto 450° C.100 1-o Ditto 500° C. 100

Production of Anode Plates

[0048] In production of anode plates, first, there were added, to a leadpowder, 0.3% by weight of lignin, 0.2% by weight of barium sulfate orstrontium sulfate, and 0.2 to 1.0% by weight of one of theabove-mentioned simple substance- and/or compound-loaded carbon powdersof the present invention, followed by kneading using a kneader for about10 minutes, to prepare various mixtures. Then, each of the resultinglead powder mixtures was kneaded with 13% by weight, based on the leadpowder, of diluted sulfuric acid (specific gravity: 1.26, 20° C.) and12% by weight, also based on the lead powder, of water to preparevarious anode active material pastes. 73 g of each anode active materialpaste was filled in a collector which was a lattice-shaped material madeof a lead-calcium alloy. The paste-filled collector was allowed to standfor 18 hours at 50° C. at a humidity of 95% for aging and then allowedto stand for 2 hours at 110° C. for drying, to produce various anodeplates before formation.

Production of Cathode Plate

[0049] In production of a cathode plate, first, a lead powder waskneaded with 13% by weight, based on the lead powder, of dilutedsulfuric acid (specific gravity: 1.26, 20° C.) and 12% by weight, alsobased on the lead powder, of water to prepare a cathode active materialpaste. Then, 85 g of the cathode active material paste was filled in acollector which was a lattice-shaped material made of a lead-calciumalloy. The paste-filled collector was allowed to stand for 18 hours at50° C. at a humidity of 95% for aging and then allowed to stand for 2hours at 110° C. for drying, to produce a cathode plate beforeformation.

Production of Batteries and Formation Thereof

[0050]FIG. 1 is a drawing showing an embodiment of the presentinvention. Six anode plates before formation 1 and five cathode platesbefore formation 2 were laminated via separators 3 made of a glassfiber; the plates of same polarity were connected with each other usingstraps to form a group of electrodes 4. 5 is a cathode strap and 6 is ananode strap. Eighteen groups of electrodes 4 were connected in series ina battery case 7, after which an electrolytic solution of dilutedsulfuric acid having a specific gravity of 1.05 at 20° C. was pouredinto the case to form various batteries before formation. Each batterybefore formation was subjected to formation at 9 A for 42 hours; then,the electrolytic solution was discharged; and a different electrolyticsolution of diluted sulfuric acid having a specific gravity of 1.28 at20° C. was poured. A cathode terminal 8 and an anode terminal 9 werewelded; a cover 10 having an exhaust valve was fitted for sealing;thereby, various lead-acid batteries were completed. Each battery had acapacity of 18 Ah and the average discharge voltage was 36 V.

[0051] A battery having a discharge voltage of 36 V and a chargingvoltage of 42 V is called a 42 V battery. In the present invention,however, the voltage range is not restricted thereto. An intendedvoltage can be achieved by connecting a plurality of single batteries inseries. In the Examples of the present invention, 42 V batteries wereproduced and the characteristics of the present invention are not variedin this voltage range.

[0052] A high-efficiency charging characteristic test was conducted asfollows. First, each lead-acid battery obtained was subjected toconstant-current constant-voltage charging for 16 hours at a chargingcurrent of 6 A and at an upper limit voltage of 44.1 V; then, dischargedat a discharge current of 4 A until a discharge voltage of 31.5 V isreached, to confirm the discharge capacity of the battery.Constant-current constant-voltage charging was again conducted for 16hours at a charging current of 6 A and at an upper limit voltage of 44.1V; then, 10% of the above-confirmed discharge capacity was discharged ata discharge current of 4 A, to set the scale of charging (SOC) of thebattery at 90%. There was measured a charging voltage Vc when chargingwas conducted for 30 seconds from the 90% SOC at a charging current of40 A.

[0053] As the charging reaction proceeds, the charging voltage Vcincreases and also hydrogen gas is generated from the anode by theelectrolysis of water. The amount of the hydrogen gas generatedincreases with an increase in the charging voltage Vc and, finally,water is exhausted. Therefore, the charging voltage Vc inevitably has anupper limit, and it is necessary to control at a voltage lower than theupper limit. In the battery tested, the upper limit voltage at which theamount of the hydrogen gas generated reaches the allowable limit, is 45V and the upper limit voltage at which no hydrogen gas generation takesplace, is 43.2 V; therefore, evaluation of the battery was made usingthese values as a standard. That is, a battery of lower charging voltageis better.

[0054] In FIG. 2 is shown a relation between the Ni content (ppm) in thenickel-loaded acetylene black fired in the air and charging voltage Vc.In any Ni content, the charging voltage Vc was lower than 45 V, i.e. theupper limit voltage at which the amount of the hydrogen gas generatedreached the allowable limit, and a good high-efficiency chargingcharacteristic was obtained. Particularly in a Ni content range of 10 to5,000 ppm, the charging voltage Vc was lower than 43.2 V, and a verygood high-efficiency charging characteristic was obtained. In a Nicontent range of 50 to 1,000 ppm, the charging voltage Vc was 43 V orlower, and a further superior high-efficiency charging characteristicwas obtained.

[0055] In FIG. 3 is shown a relation between the firing temperature ofthe nickel-loaded acetylene black fired in nitrogen and charging voltageVc. In any temperature, the charging voltage Vc was lower than 45 V, anda good high-efficiency charging characteristic was obtained.Particularly when the firing temperature was 350 to 400° C., thecharging voltage Vc was lower than 43.2 V, and a further superiorhigh-efficiency charging characteristic was obtained. The NiO ormetallic Ni in the loaded materials fired in a temperature range of 350to 400° C. had an average primary particle diameter of 0.1 to 1,000 nmas measured by TEM.

[0056] In FIG. 4 is shown a relation between the firing temperature ofthe nickel-loaded acetylene black fired in hydrogen and charging voltageVc. In any temperature, the charging voltage Vc was lower than 45 V, anda good high-efficiency charging characteristic was obtained.Particularly when the firing temperature was around 450° C., thecharging voltage Vc was lower than 43.2 V, and a further superiorhigh-efficiency charging characteristic was obtained. The Ni as theloaded material fired at around 450° C. had an average primary particlediameter of 0.1 to 1,000 nm as measured by TEM.

COMPARATIVE EXAMPLE 1

[0057] Using an acetylene black not loaded with any simple substance orany compound, a lead-acid battery was produced in the same manner as inExample 1, and its high-efficiency charging characteristic wasevaluated. The Ni content in this acetylene was less than 1 ppm, thatis, below the detection limit as measured by ICP spectrometry. Thecharging voltage Vc increased to 48 V, which was higher than the upperlimit voltage 45 V, and the high-efficiency charging characteristic wasinferior.

EXAMPLE 2

[0058] Using, as a carbon powder, various carbons shown in Table 2,nickel-loaded carbons were produced in the same manner as in Example 1.

[0059] Lead-acid batteries were produced in the same manner as inExample 1 and measured for high-efficiency charging characteristic.Their charging voltages Vc are shown in Table 2. With all the carbons,the charging voltages Vc were below 45 V and good high-efficiencycharging characteristics were obtained. Also, with mixed carbon systemsthereof, the charging voltages Vc were below 45 V and goodhigh-efficiency charging characteristics were obtained. TABLE 2 Amountof Primary Specific dibutyl Loaded particle surface phthalate ApparentCharging Ni diameter area absorbed density voltage amout Kind of carbon(nm) (m²/g) (cm³/100 g) (g/dm³) Vc(V) (ppm) Carbon black 30 1270 495 11544.5 10000 Ditto 11 362 270 109 44.8 15000 Ditto 30 254 174 270 43 750Ditto 15 1475 330 152 43.1 1000 Ditto 13 560 91 400 43.7 1500 Ditto 20140 117 310 44.3 5 Natural graphite 44 8000 Artificial graphite 44.525000 Pyrolytic carbon 44.1 12000 Coke 43.8 6000 Isotropic graphite 43.1300 Mesophase carbon 43 950 Pitch-based carbon 44.5 50000 fiber Carbonfiber by vapor 43.3 7000 phase growth Carbon fluoride 43.1 4000 Nanocarbon 43 800 Active carbon 43.1 750 Active carbon fiber 43 1000PAN-based carbon fiber 44.2 20000 Pitch-based carbon 44 10000 fiber

COMPARATIVE EXAMPLE 2

[0060] Various carbons not loading any simple substance or compound,shown in Table 3 were measured for Ni content by ICP spectrometry. TheNi contents in all the carbons were less than 1 ppm and below thedetection limit. Using these carbons, lead-acid batteries were producedin the same manner as in Example 1, and their high-efficiency chargingcharacteristics were evaluated. Their charging voltages Vc were higherthan 45 V and their high-efficiency charging characteristics wereinferior. TABLE 3 Amount of Primary Specific dibutyl Loaded particlesurface phthalate Apparent Charging Ni diameter area absorbed densityvoltage amout Kind of carbon (nm) (m²/g) (cm³/100 g) (g/dm³) Vc(V) (ppm)Carbon black 30 1270 495 115 46.7 0 Ditto 11 362 270 109 46 0 Ditto 30254 174 270 48.5 0 Ditto 15 1475 330 152 49 0 Ditto 13 560 91 400 48.8 0Ditto 20 140 117 310 47 0 Natural graphite 46.2 0 Artificial graphite48.4 0 Pyrolytic carbon 49.5 0 Coke 49.1 0 Isotropic graphite 48 0Mesophase carbon 46.8 0 Pitch-based carbon 48.3 0 fiber Carbon fiber byvapor 48.1 0 phase growth Carbon fluoride 47 0 Nano carbon 46.7 0 Activecarbon 48 0 Active carbon fiber 48.5 0 PAN-based carbon fiber 46.5 0Pitch-based carbon 49.6 0 fiber

EXAMPLE 3

[0061] Various active carbons were used as a carbon. The contents of Cu,Ni, Mn, Al, Si, K and Mg in the active carbons were measured by ICPspectrometry and are shown in Table 4. Using these active carbonscontaining various amounts of impurities, lead-acid batteries wereproduced in the same manner as in Example 1, and their high-efficiencycharging characteristics were evaluated. Their charging voltages Vc areshown in Table 4. All the charging voltages Vc were lower than 45 V andtheir high-efficiency charging characteristics were good. TABLE 4Charging voltage Cu Ni Mn Al Si K Mg Vc Symbol (ppm) (ppm) (ppm) (ppm)(ppm) (ppm) (ppm) (V) 4-a 5 50 10 <1 <1 90 <1 43.1 4-b <1 2200 <1 10 <14800 <1 43.1 4-c 500 1050 850 <1 1400 <1 <1 43 4-d 55 75 75 <1 <1 105250 43 4-e <1 <1 <1 360 <1 <1 <1 44.8 4-f <1 <1 <1 <1 <1 <1 150 44.1

EXAMPLE 4

[0062] Active carbons produced from a coconut husk were used as acarbon. A coconut husk as a raw material for active carbons was washedwith 1 N (mole/liter) hydrochloric acid for time lengths shown in Table5, then washed with water until the pH of the washings became 7 anddried, and thereafter fired to produce active carbons. The Cu contentsin these active carbons as measured by ICP spectrometry are shown inTable 5. Using these active carbons produced from a coconut husk,containing various levels of Cu, lead-acid batteries were produced inthe same manner as in Example 1, and their high-efficiency chargingcharacteristics were evaluated. Their charging voltages Vc are shown inTable 5. In all the Cu contents, the charging voltages Vc were lowerthan 45 V and good high-efficiency charging characteristics wereobtained. In a Cu content range of more than 5 ppm and less than 15,000ppm, the charging voltage Vc was lower than 43.2 V, and thehigh-efficiency charging characteristic was further better. TABLE 5 Timeof washing Charging in the voltage hydrochloric Cu Ni Mn Al Si K Mg VcSymbol acid (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (V) 5-a  1 minute15000 5600 5600 120000 11000 25000 49000 43.5 5-b 10 minutes 4800 15001500 85000 3300 3900 3700 43.1 5-c 30 minutes 1200 680 680 19000 17001400 2200 43 5-d 45 minutes 510 75 75 4200 570 410 250 43 5-e  1 hour 19<1 <1 360 82 <1 <1 43 5-f  3 hours 5 <1 <1 50 11 <1 <1 44.2

EXAMPLE 5

[0063] On the various kinds of carbon blacks shown in Table 3 wereloaded the various kinds of simple substances and/or compounds shown inTable 6. The loaded forms of the simple substances and compounds wereconfirmed by X-ray diffractometry to be a simple substance, an oxide, asulfate, a hydroxide, a carbide, or a mixture thereof, as shown in Table6. Then, lead-acid batteries were produced in the same manner as inExample 1, and their high-efficiency charging characteristics wereevaluated. In FIG. 5 are shown relations between the content of eachloaded element and the charging voltage Vc obtained. All the chargingvoltages Vc show good high-efficiency charging characteristics. In aloaded element content range of 10 to 5,000 ppm, the charging voltage Vcwas lower than 43.2 V and a strikingly good high-efficiency chargingcharacteristic was obtained. In a loaded element content range of 50 to1,000 ppm, the charging voltage Vc was 43 V or lower and a furthersuperior high-efficiency charging characteristic was obtained. Also insystems using a plurality of the above simple substances and/orcompounds, the charging voltages Vc were lower than 45 V and goodhigh-efficiency charging characteristics were obtained. TABLE 6 Kind ofloaded Symbol element Loaded form 6-a Mo MoC 6-b Co Co + CoO 6-c BaBaSO₄ 6-d Mn MnSO₄ + Mn(OH)₂ + MnOOH 6-e Sr SrSO₄ 6-f Cu Cu

EXAMPLE 6

[0064] On the various kinds of carbon blacks shown in Table 3 wereloaded the various kinds of simple substances and/or compounds shown inTable 7. The loaded forms of the simple substances and compounds wereconfirmed by X-ray diffractometry to be a simple substance, an oxide, asulfate, a hydroxide, a carbide, or a mixture thereof, as shown in Table7. Then, lead-acid batteries were produced in the same manner as inExample 1, and their high-efficiency charging characteristics wereevaluated. In Table 7 are shown the charging voltages Vc obtained. Allthe charging voltages Vc were lower than 45 V and good high-efficiencycharging characteristics were obtained. Also in systems using aplurality of the above simple substances and/or compounds, the chargingvoltages Vc were lower than 45 V and good high-efficiency chargingcharacteristics were obtained. TABLE 7 Charging Kind of loaded voltageSymbol element Loaded form Vc (V) 7-a Hf HfC 44.3 7-b Nb NbC 43.5 7-c TaTa 43.8 7-d W WC 44.1 7-e Ag Ag 43.2 7-f Zn ZnSO₄ 43.8 7-g V V₂O₅ 44.67-h Cs Cs₂SO₄ 44.5 7-i Rb Rb₂SO₄ 43.2 7-j K + Na K₂SO₄ + NaSO₄ 43.1 7-kCo + Mo Co(OH)₂ + MoO₃ 43

EXAMPLE 7

[0065] 1% by weight, based on an acetylene black, of one of thecatalysts shown in Table 8 was added to the acetylene black, followed bythorough mixing in a mortar, to prepare various carbon blacks eachcontaining a simple substance and/or a compound(s) having a catalysisfor desulfurization or SO_(x) oxidation. Various lead-acid batterieswere produced in the same manner as in Example 1 and evaluated forhigh-efficiency charging characteristic. All of the batteries showedcharging voltages lower than 45 V and had good high-efficiency chargingcharacteristics. Particularly when there were used catalysts forpetroleum refining, fuel oil desulfurization, gas production,desulfurization or deodorization for pollution control, or sulfuric acidproduction, the charging voltages Vc were lower than 43.2 V andstrikingly good high-efficiency charging characteristics were obtained.When there were used simple substances such as Co, Mo, Ni, Zn, Cu andMn, or their compounds in catalysts for petroleum refining, fuel oildesulfurization, gas production, or desulfurization or deodorization forpollution control, or when there were used simple substances such asalkali metals, alkaline earth metals, V, Mn and rare earth elements, ortheir compounds in catalysts for sulfuric acid production, the chargingvoltages Vc were 43 V or lower and further better high-efficiencycharging characteristics were obtained. Also, in systems using aplurality of the above simple substances and/or compounds in admixtures,good high-efficiency charging characteristics were obtained. Also insystems using, as a carbon powder, any one of the carbons shown in Table3, good high-efficiency charging characteristics were obtained. TABLE 8Charging voltage Catalysis Kind of catalyst Main component(s) Vc (V)Desulfurization — Ru 44 Desulfurization Catalyst for desulfurization inpetroleum CoO, MoO₃/Al₂O₃ (carrier) 42.7 refining DesulfurizationCatalyst for desulfurization in petroleum NiO, CoO, MoO₃/Al₂O₃ (carrier)42.9 refining Desulfurization Catalyst for direct desulfurization offuel oil NiO, MoO₃/Al₂O₃ (carrier) 43 Desulfurization Catalyst forindirect desulfurization of fuel NiO, TiO₂, MoO₃/Al₂O₃ (carrier) 43 oilDesulfurization Catalyst for desulfurization in gas production C 43.2Desulfurization Catalyst for desulfurization in gas production ZnO 42.6Desulfurization Catalyst for desulfurization in gas productionCuO/active carbon (carrier) 42.8 Desulfurization Catalyst fordesulfurization in gas production Fe 43.2 Desulfurization Catalyst fordeodorization in pollution control CoO, MnO₂ 42.8 DesulfurizationCatalyst for deodorization in pollution control Co(OH)₂, MnSO₄ 42.9Desulfurization Catalyst for deodorization in pollution control Al₂O₃43.2 Desulfurization Catalyst for desulfurization in petroleum NiO, CoO,MoO₃/Al₂O₃ (carrier) 43 refining SO_(x) oxidation Catalyst for sulfuricacid production V₂O₅, K₂SO₄, SiO₂ 42.9 SO_(x) oxidation Catalyst forsulfuric acid production V₂O₅ 43 SO_(x) oxidation Catalyst for sulfuricacid production Cs₂SO₄, Rb₂SO₄, CeO₂ 43 SO_(x) oxidation Catalyst forsulfuric acid production BaSO₄, MnSO₄, La₂O₃ 43 SO_(x) oxidation —MgSO₄, Pt 43.3 SO_(x) oxidation — Al₂(SO₄)₃ 44.5

[0066] With elements of low hydrogen overvoltage, such as Ni, Co, Mo, Cuand the like, hydrogen generation takes place simultaneously with thecharging reaction. FIG. 6 shows a model of the reaction mechanism. Watermolecules in an electrolytic solution are dissociated on theabove-mentioned element and the generated hydrogen ion is once adsorbedthereon. The sulfate ion generated by the dissolution of lead sulfate isalso adsorbed thereon, and is bonded with the hydrogen ion to becomeHSO₄ ⁻, which is released into the electrolytic solution. Meanwhile, thelead ion generated also by the dissolution of lead sulfate acceptselectrons from carbon and deposits as metallic lead. In this way, thecharging reaction proceeds easily and resultantly the lead-acid batteryshows a good high-efficiency charging characteristic. Therefore, evenwith simple substances or their compounds, other than those shown above,having a catalysis for desulfurization, a reaction proceeds in the samemechanism as above, and the lead-acid battery shows a goodhigh-efficiency charging characteristic.

[0067] With simple substances or their compounds, which are easilyconverted into the respective sulfates, such as V, Mn, alkali metals,alkaline earth metals, rare earth elements and the like, sulfationproceeds in the battery. FIG. 7 shows a model of this reactionmechanism. The sulfate ion generated by the dissociation of lead sulfateis adsorbed on the above-mentioned element and is easily taken into thesimple substance or compound of the element. Meanwhile, the lead iongenerated also by the dissolution of lead sulfate accepts electrons fromcarbon and deposits as metallic lead. In this way, the charging reactionproceeds easily and resultantly the lead-acid battery shows a goodhigh-efficiency charging characteristic. Therefore, even with simplesubstances or their compounds, other than those shown above, having acatalysis for SO_(x) oxidation, a reaction proceeds in the samemechanism as above, and the lead-acid battery shows a goodhigh-efficiency charging characteristic.

EXAMPLE 8 Evaluation of Single Electrodes

[0068] The simple substances, oxides, sulfates, hydroxide or carbidesshown in Table 9 were added to or loaded on an acetylene black singly orin combination, in an amount of 4,000 to 5,000 ppm based on theacetylene black, to prepare various carbon powders. 0.5% by weight ofeach carbon powder was added to a lead powder, followed by pressuremolding, to produce various acting electrodes. Using one of the actingelectrodes, a platinum wire as an opposite electrode, a silver/silverchloride electrode as a reference electrode and, as an electrolyticsolution, diluted sulfuric acid having a specific gravity of 1.26 at 20°C., a cyclic voltammogram was determined. The scanning speed was 50mV/min and the scanning potential was −800 mV to −200 mV (based on thesilver/silver chloride electrode). Before the test, a reductiontreatment of 5 minutes was conducted at −1,400 mV (based on thesilver/silver chloride electrode). With respect to the current-potentialcharacteristic examined, the current density taken as the axis ofordinate was expressed as log |I| (an absolute value in log). Theminimum value of log |I| indicates a potential at start of charging anda potential at start of discharge, and the potential at start ofcharging and the potential at start of discharge were expressed by Ecand Ed, respectively.

[0069]FIG. 8 shows the current-potential characteristics of a Ni-addedcarbon-containing electrode and a non-added carbon-containing electrode.When the potential at start of charging is expressed by Ec and thepotential at start of discharge is expressed by Ed, a relation of Ec>Edresults in the Ni-added carbon. This indicates that charging startsearlier, passivation of lead sulfate does not proceed even when completedischarge is conducted, and charging acceptability is strikinglyimproved. Meanwhile, in the case of the non-added carbon, a relation ofEc<Ed appears which is opposite to the case of the Ni-added carbon. Thisindicates that start of charging is slow, passivation proceeds whencomplete discharge is conducted, and charging acceptability isstrikingly low.

[0070] In Table 9 are shown evaluation results on the relations of Ecand Ed determined for various carbons each containing a simple substanceor a compound(s). Those carbons showing the relation of Ec>Ed areimproved in charging acceptability and therefore are rated as ◯, and acarbon showing the relation of Ec<Ed is inferior in chargingacceptability and therefore is rated as X. Superior in chargingacceptability were simple substances or compounds, of Hf, Nb, Ta, W, Ag,Zn, Ni, Co, Mo, Cu, V, Mn, Ba, K, Cs, Rb, Sr and Na. TABLE 9 Kind ofloaded Charging element Loaded form acceptability Hf HfC ◯ Nb NbC ◯ TaTa ◯ W WC ◯ Ag Ag ◯ Zn ZnSO₄ ◯ V V₂O₅ ◯ Cs Cs₂SO₄ ◯ Rb Rb₂SO₄ ◯ K + NaK₂SO₄ + NaSO₄ ◯ Co + Mo CoO + MoO₃ ◯ Ni Ni(OH)₂ ◯ Cu CuO ◯ Mn MnSO₄ ◯Ba + Sr BaSO₄ + SrSO₄ ◯ No loading — X

EXAMPLE 9

[0071] In Table 10 are shown relations between the content of impurities(e.g. Cu) in carbon blacks and charging voltage showing high-efficiencycharging characteristic of a lead-acid battery using the carbon blacks,obtained when various carbon blacks were used as a carbon. In Table 10are shown the contents of copper, nickel, manganese, aluminum, silicon,potassium and zinc determined by ICP spectrometry. Using various carbonblacks different in impurity content in place of simple substance and/orcompound-loaded carbons, lead-acid batteries were produced in the samemanner as in Example 1, and measured for high-efficiency chargingcharacteristic. The charging voltages Vc in Table 10 show thehigh-efficiency charging characteristics of the resultant batteries. Ineach of the batteries, the charging voltage Vc was lower than 45 V andthe high-efficiency charging characteristic was good. Particularly inthe furnace blacks having a total content of Ni, Cu, Zn and Mn more than1 ppm but less than 1,000 ppm, the charging voltages Vc were lower than43.2 V and the high-efficiency charging characteristics were furthersuperior. TABLE 10 Charging Cu Ni Mn Al Si K Zn voltage Vc (ppm) (ppm)(ppm) (ppm) (ppm) (ppm) (ppm) (V) Carbon black 1050 520 360 <1 <1 28 <144.7 (furnace black) Carbon black 110 30 450 510 <1 155 310 43.1(furnace black) Carbon black <1 <1 <1 <1 13 <1 <1 44.5 (acetylene black)Carbon black 50 40 100 <1 <1 <1 12 43.1 (furnace black) Carbon black 191 <1 4 <1 <1 <1 43.1 (furnace black) Carbon black <1 8 <1 <1 <1 <1 <143.1 (furnace black)

[0072] Thus, according to the present invention, a lead-acid battery ofsuperior high-efficiency charging characteristic can be obtained byusing a carbon containing a simple substance or a compound, both havinga catalysis. There can also be obtained a carbon material for use in alead-acid battery of strikingly improved charging acceptability.

[0073] It should be further understood by those skilled in the art thatthe foregoing description has been made on embodiments of the inventionand that various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and the scope of theappended claims.

What is claimed is:
 1. A lead-acid battery comprising an anode, acathode and an electrolytic solution, wherein into the anode is added acarbon containing a simple substance and/or a compound, both having acatalysis for desulfurization or SO_(x) oxidation.
 2. A lead-acidbattery according to claim 1, wherein the simple substance and/or thecompound is at least one major component constituting catalysts fordesulfurization or deodorization selected from catalysts for petroleumrefining, catalysts for fuel oil desulfurization, catalysts for gasproduction and catalysts for pollution control.
 3. A lead-acid batteryaccording to claim 2, wherein the component is at least one simplesubstance selected from the group consisting of Co, Mo, Ni, Zn, Cu andMn, or at least one oxide, sulfate or hydroxide thereof.
 4. A lead-acidbattery according to claim 1, wherein the simple substance and/or thecompound is at least one major component constituting catalysts forsulfuric acid production.
 5. A lead-acid battery according to claim 4,wherein the component is at least one simple substance selected from thegroup consisting of alkali metals, alkaline earth metals, V, Mn and rareearth elements, or at least one oxide or sulfate thereof.
 6. A lead-acidbattery comprising an anode, a cathode and an electrolytic solution,wherein into the anode is added a loaded material obtained by loading,on a carbon, at least one simple substance selected from the groupconsisting of Hf, Nb, Ta, W, Ag, Zn, Ni, Co, Mo, Cu, V, Mn, Ba, K, Cs,Rb, Sr and Na, or at least one oxide, sulfate, hydroxide or carbidethereof.
 7. A lead-acid battery according to claim 6, wherein the loadedmaterial is obtained by loading, on a carbon, at least one simplesubstance selected from the group consisting of Ni, Co, Mo, Cu, V, Mn,Ba, K, Cs, Rb, Sr and Na, or at least one oxide, sulfate, hydroxide orcarbide thereof.
 8. A lead-acid battery according to claim 6, whereinthe at least one element is loaded on the carbon in an amount of 10 to5,000 ppm by weight per element.
 9. A lead-acid battery according toclaim 6, wherein the at least one element is loaded on the carbon in anamount of 50 to 1,000 ppm by weight per element.
 10. A lead-acid batteryaccording to claim 6, wherein the simple substance, oxide, sulfate,hydroxide or carbide has an average primary particle diameter of 0.1 to1,000 nm.
 11. A lead-acid battery according to claim 1, wherein thecarbon is at least one member selected from the group consisting ofcarbon black, acetylene black, natural graphite, artificial graphite,pyrolytic carbon, coke, isotropic graphite, mesophase carbon,pitch-based carbon fiber, carbon fiber by vapor phase growth, carbonfluoride, nanocarbon, active carbon, active carbon fiber and PAN-basedcarbon fiber.
 12. A lead-acid battery according to claim 6, wherein thecarbon is at least one member selected from the group consisting ofcarbon black, acetylene black, natural graphite, artificial graphite,pyrolytic carbon, coke, isotropic graphite, mesophase carbon,pitch-based carbon fiber, carbon fiber by vapor phase growth, carbonfluoride, nanocarbon, active carbon, active carbon fiber and PAN-basedcarbon fiber.
 13. A lead-acid battery comprising a cathode, an anode andan electrolytic solution, wherein into the anode is added an activecarbon or a carbon black or a mixture thereof containing at least onesimple substance selected from the group consisting of Cu, Ni, Zn, Mn,Al, Si, K and Mg, or at least one compound thereof.
 14. A lead-acidbattery according to claim 13, wherein the active carbon is an activecarbon produced from coconut husk, having a Cu content of more than 5ppm by weight but less than 15,000 ppm by weight.
 15. A lead-acidbattery according to claim 13, whrein the carbon black is a furnaceblack having a total content of Ni, Cu, Zn and Mn more than 1 ppm byweight but less than 1000 ppm by weight.
 16. A carbon material for usein a lead-acid battery, which is a carbon powder containing or loadingthereon at least one simple substance selected from the group consistingof Hf, Nb, Ta, W, Ag, Zn, Ni, Co, Mo, Cu, V, Mn, Ba, K, Cs, Rb, Sr andNa, or at least one oxide, sulfate, hydroxide or carbide thereof.
 17. Acarbon material for use in a lead-acid battery, which is a carbon powdercontaining a simple substance and/or a compound, both having a catalysisfor desulfurization or SO_(x) oxidation.
 18. A carbon material for usein a lead-acid battery, which is an active carbon and/or carbon blackcontaining at least one simple substance selected from the groupconsisting of Cu, Ni, Zn, Mn, Al, Si, K and Mg, or at least one compoundthereof.